Charge forming means



July 15, 1958 J. DOLZA CHARGE FORMING MEANS Filed Sept. 10, 1956 4 Sheets-Sheet 1 A TTOPNE Y July 15, 1958 J. DOLZA CHARGE FORMING MEANS 4 Sheets-Sheet 2 Filed Sept. 10, 1956 IN V EN TOR. Y fa/fizz fla/za I p I A 7' TOR/V5 Y 7 4 Sheets-Shae; 5

IN VEN TOR. W -/Z2/2/2.@o/za A TTOR/VE Y July 15, 1958 JJDOLZA CHARGE FORMING MEANS Filed Sept. 10, 1956 Q, M k% m Q xx & QM Q \4 Q. a n O l. l I x n 2 0 wwm kg \i I w \NN ww & R 2% Q Q July 15, 1958 4.001. 2,843,098

CHARGE FORMING MEANS F'iled Sept. 10, 1956 4 Sheets-Sheet 4 if 1/ M Z IN VEN TOR.

A T TOR/V5 Y United States Patent CHARGE FORMING lVIEANS John Dolza, Fenton, Mich, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application September 10, 1956, Serial No. 608,853

11 Claims. (Cl. 123-119) The present invention relates to charge forming means for internal combustion engines and more particularly to means for injecting metered quantities of fuel into the charge for such an engine.

In the past it has been customary on internal combustion engines for use on mass produced automotive vehicles to employ one or more carburetors and an intake manifold for charging the cylinders. Although such arrangements in the past have been found satisfactory, in order to attain the required performance from such an engine, the manifolds and carburetors have become increasingly more complex and therefore more expensive and troublesome in operation. Accordingly, in order to improve the performance of such engines numerous attempts have been made to devise a fuel injection system capable of accurately metering fuel and injecting the fuel into the charges for the various cylinders. However, heretofore, such systems have been excessively delicate and expensive. These and other factors have made them unsuitable for use on mass produced automotive vehicles intended for passenger car use. Accordingly, such systems have never been widely adopted on automotive vehicles.

It is now proposed to provide a fuel injection system which is simple and economical to manufacture and which is particularly adapted for use on automotive vehicles. This is to be accomplished by providing a charge forming unit contained in a shroud assembly adapted to be secured to the engine so as to replace the carburetor and intake manifold arrangement previously employed. The charge forming unit will not only provide a compact, simplified unit in which all of the elements cooperate with each other to provide a reliable charge forming unit, but it will also greatly facilitate installation and servicing of the unit.

These and other objects and advantages of the present invention will become more fully apparent from the following specification and drawings.

In the four sheets of drawings:

Figure l is a cross-sectional view of a charge forming unit embodying the present invention installed on an internal combustion engine and taken substantially along the plane of line 11 in Figure 2.

Figure 2 is a plan view of the charge forming unit disclosed in Figure 1.

Figure 3 is a cross-sectional view of the fuel metering mechanism employed in the fuel injection system and is taken substantially along the plane of line 33 in Figure 2.

Figure 4 is a cross-sectional view of the air meter mechanism taken substantially along the plane of line 44 in Figure 2.

Figure 5 is a fragmentary side view of a portion of the air meter disclosed in Figure 4.

Referring to the drawings in more detail the present invention may be incorporated in a charge forming unit that is adapted to be employed on an internal com bustion engine 12. Although this unit 10 may be employed on any suitable engine 12, in the present instance,

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for purposes of illustration, an engine of the so-called V-type is shown. This engine 12 employs a cylinder block 14 having a pair of angularly disposed banks 16 of cylinders 18 with an upwardly opening space therebetween. Each bank 16 includes a row of aligned cylinders 18 with a cylinder head 20 secured along the top thereof to close the ends of the cylinders 18 and thereby form the combustion chambers 22. Each of these cylinder heads 20 includes a separate intake passage 24 for each of the cylinders 18 that extend transversely therethrough. The outer ends of these passages 24 form rows of intake ports 26 along the inner sides or faces 28 of the head 20 while the opposite ends form intake valve seats 30 opening into the combustion chamber. Intake valves 32 actuated from a camshaft are provided in these seats 30 for timing the admission of the charges into the combustion chambers 22.

In order to supply the combustible charge of air and fuel flowing through the intake passages 24to the cylinders, the charge forming unit 10 includes an air induction system 34 and a fuel injection system 36 that are enclosed in a shroud 38 adapted to be removably secured to the engine 12 in the space between the two banks 16 of cylinders 18.

The shroud 38 not only encloses the charge forming unit 10 but also forms an integral part of the induction system 34. It may be fabricated from some suitable material such as sheet metal and includes a lower member 40 removably secured to the faces 28 of the cylinder heads 20 by bolts or any other suitable fastening means. Thermal insulation 42 is preferably disposed between the faces 28 and the lower member 40 for insulating the shroud 38 from the heat of the engine 12. A cover member 44 is secured to the lower member 40 to form an enlarged plenum chamber 46.

The cover member 44 may include an inlet 48 that communicates with the atmosphere to supply fresh air to the plenum chamber 46. If the engine is incorporated into an automobile or similar installation, a suitable conduit 50 may extend from the inlet 48 to the front of the vehicle for drawing fresh cool air from ahead of the radiator. In addition, a suitable air cleaner or filter 52 may be provided in the inlet 48 for removing dust, dirt, etc. from the air. The present filter 52 is an annulus of filtering material disposed in an annular chamber 54 and clamped between the two members 56. Thus atmospheric air may flow from the chamber 54 radially inwardly through the filter 52 and into the plenum chamber 46 so that all of the air in the plenum chamber 46 will be filtered.

In addition to the shroud 38 the induction system 34 may also include an intake manifold 58 and an air meter 60 disposed in the plenum chamber 46 and completely enclosed by the shroud 38. The intake manifold 58 is a rigid self-supporting structure having a main body 62 that forms a central chamber 64 and a plurality of substantially identical ram pipes 66 that extend downwardly from the main body 62 to be secured to the faces 28. The upper ends of these ram pipes 66 open into the central chamber 64 while the lower ends register with the intake ports 26 so as to form separate induction passages 68. In order to improve the performance of the engine each of these induction passages 68 may be tuned so as to tend to resonate during one or more engine operating conditions for ramming air into the engine cyinders 18.

The air meter 6*!) is mounted on an inlet 70 projecting from the side of the manifold 58 for drawing the filtered air from inside of the plenum chamber 46 and delivering it to the intake manifold 58 for distribution to the cylinders. The air meter 60 comprises a generally cylindrical housing 72 having a substantially cylindrical pas- .so as to be completely immersed in the fuel.

3 sage 74 extending axially therethrough. A throttle valve 76 is disposed in the downstream end thereof adjacent the intake manifold 58 for regulating the quantity of induction air flowing into the engine 12. Although the air meter: 68 may include any suitable metering. restriction suchas a venturi, in thepresent instance a tapered member 78 is mounted onstuds 80 to project into the inlet ,end 82 of the passage. 74. The exteriorof this member 78 is shaped to cooperate-with the interior of the passage 74 to form a metering restriction havinga cross-sectional area varying similar to that of a venturi. A flared member 84 is secured to the end of the housing 72 to rest on the seat 86 with the inner end thereof being spaced from the endrof the housing 72 to thereby form an annular port 88. This port'88 is positioned to sense the throat vacuum developed by the airflow through the air meter 60. It has been found that although this annular port 88 may be at the point of least area, it is desirable to move the port 83-slightlyposterior thereto to develope a signal which will more nearly match the desired metering characteristics.

The fuel injection system 36 may include fuel metering mechanism 96 and a transfer pump for insuring delivery ofanuninterrupted supply of fuel from a storage tank to the metering mechanism90. A diaphragm type of fuel. pump having an output-pressure of approximately p. s. i. has been found suitable for this application.

The fuel metering mechanism 91 includes a housing 94 having afloat bowl 96 and-a meteringportion 98. The

float bowl portion :96 includes an inlet 100 having a secondary filter element. 102 adapted to remove any 7 minute particles which might otherwise impair the operthe fueland cause-any vapors entrained'therein to be removed from the fuel.

The injector pump 118 which is preferably of thegear type may be located in the bottom of the float bowl 96 This will insure the pump 116 being primed at all times and permit the pumpto draw fuel from the float bowl 96 without creating any material reduction in the pressure of the ,the housing 94 to intersect'the bottom of a cylindrical fuel distributor 116 located in the fuel meteringportion. The lower portion of this distributor 116 includes a pressure sensitive check valve 118 which is disposed inside of a valve housing 120 that is reciprocably disposed in the bottom of the cylindrical distributor passage. The valve housing 128 is biased upwardly by a spring 122 so that the tapered end 124 thereof engages the lower end of a guide member 126. The check valve includes a spring biased ball that is effective to maintain some predetermined pressure downstream thereof. After passing through the check valve 118 the fuel will divide into two parts, the surplus fuel that passes through the spill ports 128 in the guide member 126 for return to the float chamber 96 by overflowing from the linkage chamber 130 and the metered portion that flows through the outlets 132 into the distributor lines 134. The volume of the metered fuel is controlled by regulating the amount of fuel by-passed through the spill ports 128. This, in turn, is regulated by a plunger valve 136 reciprocably disposed in an axial passage through the guide member 126 and having the periphery of the lower end registering with the spill ports 128. It has been found desirable to employ a pair of distributor lines 134 as they will always symmetrically intersect the distributor chamber 116. The outerends ofthe lines 134 areconnected to-distributor A trol lever 158.

blocks 135 which are connected to injector lines 138 having injector nozzles 140 on the ends thereof for injecting the metered fuel into the charges in the induction passages 68. These nozzles 140 are all substantially identical and include a small discharge jet that is disposed in an envelope of atmospheric air. Thus the pressure in the distributing chamber 116 will be indicative of the amount of metered fuel discharged through the nozzles 140. Since the area of the piston valve 136 is subjected to this pressure, there will be a force proportional to the fuel flow tending to open the valve 136 and increase the amount of fuel by-passed through the spill ports 128.

The metering portion 98 of the fuel meter 90 also includes a diaphragm chamber 142 that is interconnected with the annular port 88 and a linkage chamber 130 that contains a linkage 144 for operatively interconnecting the diaphragm with the plunger valve 136. The linkage 144 includes a vertical pin 146 that has the upper end connected to the diaphragm 148 and extends downwardly through a small hole 150 in the cup 152 to be attached to a pivoted joint 154 between a counterweight lever 156 and a con- It has been found desirable for the pin 146 to pass through as small a hole as possible to eliminate the passage of fuel vapors into the chamber below the diaphragm 148 and also to provide a very large vent 160 to the atmosphere to quickly dissipate any fuel vapors that may enter the chamber to thereby eliminate any vapor pressure effects upon the diaphragm'148. The counterweight lever 156 is pivoted about a fixed pin 162 while the control lever- 158 rotates about the end of an adjustable mixture control arm or ratio arm 164 so that that;the outer end thereof rests on and tends to depress the plunger valve 136 to close the spill ports 128.

It may thus be seen that as the induction air passes through the air meter 60 a vacuum signal will be trans- 1 mitted to the diaphragm chamber 142 so as to act on the diaphragm 148 and by means of the linkage 144 produce a downward force on the plunger valve 136 in opposition to the upward force on the plunger valve 136 produced by the fuel pressures. These opposed forces will cause the plunger 136 to move axially to increase or decrease the amount of spill fuel until the two forces are in balance. Under these circumstances the air and metered fuel will be flowing in some predetermined proportions. These proportions will be determined by the mechanical advantage of the linkage 144 which, of course, is regulated by the position of the ratio arm 164 which forms the fulcrum for the control lever 158.

Normally an internal combustion engine such as employed in an automotive vehicle operates at part load and is seldom required to develop maximum power. Accordingly, it is highly desirable to normally supply a lean charge suitable for maximum economy and to only supply a richer charge suitable for maximum power under those circumstances where maximum power is required and economy is of secondary importance. Although there ,are numerous, ways in which this objective may be accomplished it is advantageous to retain the mixture control arm 164 normally positioned for maximum economy and to provide maximumpower enrichment means 168 for moving the arm 164 to a position producing a rich mixturesuitable for maximum power. It has been found that during part load operation there is a considerable induc- --76 so as to sense the induction vacuum. The diaphragm 170 is connected to a crank 181 effective to position the ratio-arm "164. --A rich -stop= 182 and a lean stop184 around the check valve 118.

. chamber.

are provided to engage the crank'181 to limit the swingingmovement thereof. When the crank 181 is against the lean stop 184 the ratio arm 164 will be positioned so that the mechanical advantage of the linkage 144 will insure a lean charge suitable for maximum economy.

When the crank 181 engages the other stop 182 the linkage 144 will be adjusted for a maximum economy charge. A spring 186 biases the diaphragm 170 in opposition to the vacuum and does not have sulficient strength to overcome the vacuum except when it is small for maximum power. Thus normal induction vacuum will retain the crank 181 against the lean' stop 184, thereby insuring a charge suitable for maximum economy. However, when the throttle 76 approaches the fully opened position and the intake vacuum is very small, the spring 186 will force the diaphragm 170 outwardly and cause the crank 181 to move against the maximum power step 182. This be operatively interconnected with the starting motor to be operative only whenever the starting motor is energized. This means 188 will be efiective to permit the in jector pump 110 to pump the fuel into the charges more easily by substantially eliminating the pressure drop at the check valve 118 and also to insure all of the fuel that is discharged from the injector pump 110 beingdelivered to the charges.

In the present instance this starting enrichment means 188 includes an electrical solenoid 190 which is secured to the fuel meter housing 94 and is operatively interconnected with the electric circuit for the starting motor.

This solenoid 190includes a vertical plunger 192 that has the upper end thereof operatively interconnected with an enrichment arm' 194 disposed inside of the linkage chamber 130. This arm 194 is mounted to pivot about a fixed pin 196 and has one end thereof disposed immediately above the end of the control arm 158. When the solenoid 190 is deenergized, as it normally is, the plunger 192 is retracted and the enrichment arm 194 is spaced from the end of the controlarm 158. However, when the solenoid 190 is energized, as a result of actuating the starter, the plunger 192 will be'extended, thereby causing the enrichment arm 194 to rotate about the pin 196 with the other end striking the end of the control arm 158. This will force the control arm 158 and plunger valve 136 downwardly until it engages the projection 198 on the end of the valve housing 120 and depresses the housing 120 away from the guide member 126. This will not only adjusting screw 228.

close the spill ports 128 but will also unseat the housing 1 120 from the guide member 126 and open a bypass Consequently, thefuel from the injector pump 110 may by-pass the check valve 118 without being subject to the pressure loss required to open the valve 118. In addition, all of the fuel delivered to the distributing chamber 116 will be distributed to the cylinders.

It will thus be seen that during the starting operation when the starting motor will be energized, the solenoid 190 will also be energized. This will simultaneously open a by-pass around the check valve 118 and close thespill ports 128. Accordingly, during the cranking operation the entire output from the injector pump 110 will flow,

into the distributing chamber 116 without being opposed by the check valve 118. In addition, all of the fuel from the pump 110 will be distributed to the cylinders without any fuel being by-passed for return to the float As soon as the engine commences running under its own power, the cranking motor will be deenergized together with the solenoid 190. This will retract thesolenoid plunger 192 and restore the normal metering action.

. After the engine has become operative and 1s running under its own power; the metering mechanism 90 will beset for normal operation and will meter the fuel in proportion to the air flow for producing an economy charge. However,- when the temperature of the engine is below normal such a charge does not produce satisfactory operation of the engine and, accordingly, it is desirable to provide a charge having slightly richer proportions than is normally supplied by the metering means 90. Accordingly, a thermostatic enrichment means 200 may be provided for enrichment of the charge during subnormal temperatures.

In the present instance this enrichment means 200 includes a housing 202 enclosing a vent valve 204 and a thermostatic spring element 206 that controls the valve 204. The valve 204 which is connected to the spring element 206 by means of an arm 208 and link 210 having a lost motion connection 212 therebetween includes a sliding plunger 214 disposed in a cylindrical bore 216. One end of the bore 216 is vented to atmosphere by a vent port 218 while the other end is interconnected with the fitting 176 in the side of the air meter 60. This is the fitting 176 that senses induction vacuum and is connected to the maximum power diaphragm chamber 174 by an enrichment vacuum line 178. Although the thermostatic spring element 206 may be heated by the engine, it has been found advantageous to heat the spring by an electrical heating element 220 that is operative only when the engine is running. In the present instance the heating element 220 is interconnected with the electrical system of the engine so as to be energized when the generator is in operation. In addition to the foregoing arrangement, it has been found desirable to employ a fast idle cam 222 for positioning the throttle valve when the temperature is subnormal. This cam 222 is positioned by a link 224 connected to the arm 208 and includes a stepped surface 226 on the periphery that may engage the If desired, the lost motion connection 212 may be provided to allow the fast idle and/ or enrichment action to be maintained for different periods.

When the thermostatic spring 206 is heated to some predetermined amount the fast idle earn 222 will be moved clear of the set screw 228 and the vent valve 204 will be closed. Accordingly, normal metering action will be maintained. However, if the thermostatic spring 206 is cold the fast idle cam 222 will be positioned to engage the set screw 228 and limit the closing movement of the throttle valve 76 and also the vent valve 204 will be open. As a result; atmospheric air may bleed through the vent orifice 218 and into the fitting 176. Thus even Of course, as soon as the heating element 220 warms up the thermostat 206, the vent valve 204 will close and the normal metering action will be restored.

During idling operation of the engine the air flow will be very small and the vacuum signal developed in the throat of the air meter 60 will normally be very weak and not suitable for use as a metering signal in the idle and offidle range. Accordingly, an-idle and off idle enrichment means 230 may be provided for producing a metering signal that will accurately control the metering action. This means 230 includes an auxiliary or idle air supply passage 234 that has one end 236 thereof opening into the passage 74 anterior to the throttle valve 76 and the other end 238 opening into the passage 74 posterior to the throttle valve 76 and also a pair of pressure sensing orifices 240 and 242 on the opposite sides of the throttle valve 76. The idle air supply passage 234 affords a path for by-passing idle air around the throttle valve even when the valve is closed. It has been found preferable to-regulate the idle air flow by completely closing the throttle valve 76 and providing an adjustable screw member244 in-the idle air supply pasage- 234. An adjustable stop.246 may be provided to prevent the .valve '76 sticking when it is completely closed. The two orifices-240 and 242 are interconnected with the control a :signal line by a passage 248 in the air meter housing 72. The downstream orifice 240 opens into the idle air supply I passage 234 downstream of the adjustable screw 244 so as to sense the intake vacuum. Thus when the throttle valve 76 is completely closed the high induction vacuum will be transmitted to the diaphragm chamber 142 to reinforce the signal transmitted from the annular port 88.

By the selection of a proper size of orifice and/ or making it adjustable the reinforcement of the signal will be cor- ..rect for insuring the desired idling charge. The secondary orifice 242, the orifice upstream of the throttle valve 76,

is disposed immediately ahead of the throttle 76 to register with the periphery thereof when it is in the off idle range.

Thus the air will have to flow through the restricted space between the valve 76 and the surface of the passage 74' and simultaneously across the orifice 242. This will result in a venturi effect that will be transmitted to the diaphragm chamber 142 to produce an enrichment of the charge during off idle operation.

When the load is overrunning and driving an internal combustion engine, the fuel supply to and burned in the cylinders performs no useful work and, accordingly, is wasted. In addition, there are indications that the very high induction vacuum resulting from the closed throttle valve during such operations interferes with a complete combustion of the charge. Therefore in order to effect an economy in the fuel consumption it is proposed to provide a coasting fuel shut-off means 249 for eliminat- -ing the fuel flow when the load is overrunning the engine to thereby prevent the injection of any fuel into the charge.

- The means includes a shut off valve 250 in the injector pump outlet passage 114 which is actuated by a diaphragm -252. This valve 250 is normally retained closed by a spring 254 to insure distribution of the fuel. However, when the valve 250 is opened, fuel from the injector pump 110 will be by-passed directly into the float bowl It should be noted that under such circumstances there will not be adequate pressure to open the check valve 118 and, accordingly, all fuel injection into the charge will be eliminated. -It has been found that the induction vacuum is even greater than idle vacuum when the engine is being overrun by the load. Accordingly, the

diaphragm chamber 256 above the diaphragm 252 may be interconnected with a fitting 258 on the side of the air meter 60 by a vacuum line 260. This fitting 258 communicates with the port 262 downstream of the throttle valve 76 by a drilled passage 180. A vent tube 266 upstream of the throttle valve 76 projects rearwardly so that the end thereof is positioned to engage a button 268 on the throttle valve 76 when it is in the-closed position. Thus when the throttle valve 76 is open the air may fiow through the vent tube 266 around the throttle valve 76 and out of the port 262. This will greatly reduce the amount of vacuum transmitted to the diaphragm chamber 256. However, when the throttle valve 76 is closed the button 268 will close the tube 266 and permit the induction vacuum to flow directly into the chamber 256.

"During normal operation the spring 254 will retain the v shut off valve 250 completely closed. The fuel from the injector pump 110 will then flow into the distributing chamber 116 and thereby allow the normal metering action to carry on. In the. event the throttle valve 76 is completely closed and the load is driving the engine, there will be a very high induction vacuum that will be transmitted from the port 262 through the vacuum line 260 to the diaphragm chamber 256. This vacuum signal will be I greatvenough to exert asuificient force on the diaphragm 252 to compress the spring. 254. and open the shutoff valve 250 and by-pass the fuel into the float bowl 96.

-The check valve 118 will then close and prevent the distribution of any fuel to the cylinders. It should be noted that in the event the throttle valve 76 is partially open, the button 268 on the valve 76 will disengage the end of the tube 266 and allow air to pass through the vent. tube 266. This air will flow from in front of the throttle valve 76, which is substantially atmospheric, through the vent tube 266 and out of the port 262 to thereby limit the vacuum in the diaphragm chamber 256 10 to no greater than idle vacuum. Thus as long as the operator maintains the throttle valve 76 slightly open, a

. supply of metered fuel will be insured for the engine.

It is to be understood that, although the invention has .been described with specific reference to particular embodiments thereof, it is not to be so limited since changes and alternations therein may be made which are within 'the full intended scope of this invention as defined by' the appended claims.

The claims:

1. A charge forming device for an internal combustion engine having a plurality of cylinders, said device comprising an induction arrangement for supplying induction .air to the cylinders of said engine, fuel metering means responsive to said air flow and effective to meter fuel in proportion thereto and to inject said metered fuel into said air, a shroud encompassing said means and having an inlet communicating with the atmophere to circulate air around said means in heat exchanging relation therewith.

2. A charge forming device for an internal combustion engine having a plurality of cylinders, said device comprising an induction arrangement for supplying in- .duction air to said cylinders including a throttle valve for regulating the volume of air entering said engine, fuel comprising intake manifold means communicating with said cylinders and having a throttle valve inlet for regulating the volume of air fiowi ng therethrough and into said engine, fuel metering means responsive to said air flow and effective to meter fuel in proportion thereto and to inject said metered fuel into the charge flowing through said manifold, a shroud encompassing said means and having a filtered inlet communicating with the atmosphere, said throttle inlet drawing induction air from the inside of said shroud to cause the air entering said shroud inlet to circulate around said means in heat exchanging relation therewith.

4. A charge forming device for an internal combustion engine having a plurality of cylinders, said device comprising an air metering means for regulating the volume of air entering said engine, fuel metering means operatively interconnected with said air meter and effective to meter fuel in proportion to said air flow and to inject said metered fuel into the charge for said cylinders, a shroud encompassing said means and communicating with the atmosphere to circulate cool induction air around said means in heat exchanging relation therewith.

5. A charge forming device for an internal combustion engine having a plurality of cylinders, .said device comprising induction means forsupplying throttled air to the cylinders of said engine, fuel metering means responsive to said air flow effective to meter and inject fuel jinto said charge in proportion thereto, a shroud adapted to be mounted on said engine and thermally insulated therefrom, said shroud encompassingsaid' means and having an inlet communicating with the atmosphere to circulate cool induction air around said means in heat exchanging relation therewith.

6. A charge forming device for an internal combustion engine having a plurality of cylinders, said device comprising a shroud adapted to be supported by said engine and having an intake communicating with the atmosphere to draw air therefrom, an induction means disposed inside of said shroud for supplying air to the engine cylinders and having a throttle valve inlet for drawing the induction air from inside of said shroud and regulating said flow, fuel metering means responsive to said air flow effective to meter and inject fuel into the charge in proportion thereto, said intake and inlet being arranged so that the supply of induction air will circulate around said means in heat exchanging relation therewith.

7. A charge forming device for an internal combustion engine comprising a base member mounted on said engine by thermal insulating means, an induction system disposed on said base for supplying induction air to the engine cylinders, fuel means supported on said base member responsive to said air flow for injecting metered fuel into said charge in proportion thereto, a cover member secured to said base member, said members forming a shroud enclosing said means to form a shroud having an inlet communicating with the atmosphere for supplying air thereto for circulation around said fuel metering means.

8. A charge forming device for an internal combustion engine having a plurality of cylinders, said device comprising induction means for supplying air to the cylinders of said engine and having a throttle valve inlet for regulating said flow, fuel metering means responsive to said air flow and eifective to meter fuel in proportion thereto, a shroud encompassing said means and having a filtered intake for supplying filtered induction air to the interior of said shroud to circulate in heat exchanging relation with said means before passing through said inlet.

9. Charge forming means for an internal combustion engine having a plurality of cylinders, said means comprising an intake manifold having an air meter with a throttle valve therein to regulate the air flow into said engine and a metering restriction adapted to develop a pressure differential indicative of said flow, fuel metering means operatively interconnected with said air meter 10 and responsive to said differential for metering fuel in proportion to said air flow and to inject said metered fuel into the charge, a shroud encompassing said manifold and said means and having an inlet communicating with the atmosphere to circulate cool induction air around said means in heat exchanging relation therewith.

10. In an engine having an induction system with a throttle valve inlet for supplying throttled air to the engine cylinders and fuel means for injecting metered quantities of fuel into said air, an idle system comprising an auxiliary air supply passage extending around said throttle valve with a restriction therein for regulating the amount of air flow therethrough, an orifice immediately upstream of said throttle valve positioned to register with the periphery of said throttle valve when in the off-idle position and to thereby sense the volume of air flow thereacross and to thus modify the effectiveness of said pressure signal when said valve is in the off-idle position, said orifice also communicating with said air supply passage at a point downstream of said restriction to sense the intake vacuum.

11. In an engine having an induction system including an inlet passage with a throttle valve for regulating the volume of air flow and also having fuel means for injecting metered quantities of fuel into said air, an idle system comprising an auxiliary air supply passage extending around said throttle valve with a restriction therein for regulating the amount of air flow therethrough, an orifice in the surface of said inlet passage positioned immediately upstream of said throttle valve to register with the periphery of said throttle valve when said valve is in the oil-idle position to sense the vacuum produced by the air flow thereacross, said orifice also communicating with said auxiliary air supply passage at a point downstream of said restriction to sense the intake vacuum, said sensed vacuums being effective to regulate said fuel means for metering the fuel.

References Cited in the file of this patent UNITED STATES PATENTS 2,060,498 Gobb Nov. 10, 1936 2,361,277 Mock Oct. 24, 1944 

